Gulf of Maine Warming Update: 2022 the Regions Second Warmest Year

Documenting one more year in a decade of above-average regional temperatures

Author

Adam Kemberling

Published

January 18, 2023

With an annual average sea surface temperature (SST) of 53.66°F — more than 3.72°F above normal — the Gulf of Maine experienced its 2nd warmest year on record in 2022. The region ranked in the top 3 warmest temperatures across all seasons, with the most extreme temperatures occurring in November.

Annual Sea Surface Temperatures

The annual average SST in the Gulf of Maine for 2022 was 53.66°F; this was 3.72°F above the long-term (i.e., 1982-2011) average. This year fell short of the previous warmest year on record — 2021 — by a remarkable 0.43°F. 2022 was the second hottest year on record for the Gulf of Maine, shifting the 1982-2022 warming rate to 0.86°F / Decade. Since the early 1980s, the rate of warming in the Gulf of Maine has been nearly triple that of the world’s oceans (Figure 1).

Figure 1: A timeseries of annual average sea surface temperature anomalies for the Gulf of Maine (solid black line) from 1982 through 2021, illustrating that 2021 was the warmest year on record. Long-term trendlines for the Gulf of Maine (blue) and the entire globe (green) show how much more quickly the Gulf of Maine is warming compared to the rest of the world.

The rate of warming in the region vary throughout the year. Comparisons across the four seasons (Figure 2) reveal that the Gulf of Maine is warming fastest during the Summer and Fall months (~4x the global average), nearly twice the rate seen during the spring (~2x the global average).

Figure 2: Four timeseries panels of the annual averages for each season (solid black lines) for the Gulf of Maine. Decadal trends are overlayed to compare decadal trends in the Gulf of Maine (blue) and the entire globe (green). Rates are much faster in the Gulf of Maine across all seasons, with the smallest difference in rates during the spring.

There can be significant spatial variability in annually-averaged SST patterns. The Gulf of Maine in 2022 illustrated this fact with the region southeast of Georges Bank experiencing the highest SST anomalies (Figure 3). This area is more susceptible to large-scale variability in major oceanic currents, such as the relative influence of the Gulf Stream versus the Labrador Current, than other areas of the Gulf of Maine.

Figure 3: Map of annual average sea surface temperature anomalies in 2021. The box outlined by the black dashed line denotes the region of study for the analysis presented throughout this report.

Looking at these spatial patterns at a seasonal level (Figure 4) shows just how “patchy” these pockets of above-average temperatures can be. In the spring months the areas to the south and south east of the Gulf of Maine are pocketed with a mixture of both above and below average water masses. During the summer months we can see that the water within the Gulf of Maine itself and the deeper waters just south of Georges Bank are higher than the surrounding areas. In the fall and winter the Gulf of Maine becomes less of a heat island itself, but remains hot as bands of elevated temperature water masses move up the coast nearby.

Figure 4: Map of each season’s average sea surface temperature in 2022. Winter data is still ongoing and is subject to future changes in sea surface temperature.

When we compare 2022 to other unusually warm years in the Gulf of Maine, we see that in absolute terms it was roughly half a degree from 2021’s record year. When we look at the deviation from the long-term average SST (i.e., the annual SST anomaly), the last decade stands out (Figure 5). 2022 continues a pattern that began in 2010 of sustained above-average temperatures. With the exception of 2019 (ranked 13th), all of the last ten years remain in the top 10 for SST.

Figure 5: Bar plot ranking the top 5 annual sea surface temperature (SST) values and their equivelant SST anomalies. Absolute temperatures displayed in text with the corresponding year.

Worldwide Temperatures

It was not just the Gulf of Maine that experienced exceptional warmth in 2022, however. According to NOAA, 2022 was the 2nd warmest year on record for the contiguous United States and the 3 warmest year globally for sea surface temperatures. The figure below (Figure 6) shows annual average SST anomalies for oceans all over the world in 2022. While much of the Southern Ocean and expanses of the southeastern Pacific off South America were anomalously cool (a feature of La Niña conditions), most of the world’s oceans experienced unusually warm temperatures in 2022. This is particularly true for James Bay in Canada, the Labrador Sea, the Baltic Sea, and a swath from ~35 °N to ~45 °N across ocean basins — a region that includes the Gulf of Maine.

Figure 6: Map of annual average sea surface temperature anomalies for the world’s oceans in 2022.

Daily Sea Surface Temperatures

The annual cycle of SST in the Gulf of Maine exhibits a familiar pattern with low temperatures in March and high temperatures in August (Figure 9). The average difference between the annual maximum SST in August and the annual minimum SST in March is 22.87 °F. In 2022, the difference between the maximum SST (Aug-07, 68.72°F) and minimum SST (Mar-19, 42.15°F) was 26.57 °F, with daily SST anomaly values never falling below +1.59 °F and reaching as high as +7.36 °F above the long-term average.

Record Setting Daily Temperatures

The figure below shows the highest recorded SST values for every day of the year in the Gulf of Maine. Record-setting days that occurred in 2022 are denoted with red dots (Figure 7). Indeed, record-setting daily high SSTs in the Gulf of Maine were set for more than 1/2 of all days in November and December. The most daily records were set in November, which experienced record high SSTs for 24/30 or 80% of the month. In total, 2022 set 169 record high temperature days in the Gulf of Maine; stated another way, nearly 46% of days in 2022 experienced record high SSTs in the Gulf of Maine.

Figure 7: Timeseries of the record high daily sea surface temperature in the Gulf of Maine for every day of the year. Record-breaking temperatures that were observed in r report_yr are denoted with red dots; when a record-breaking temperature for a given day was observed in any other year, that daily record is in gray.

Figure 8: A bar plot showing the percentage of days during each month in 2022 when a record-high temperature was observed in the Gulf of Maine (e.g., 80% — 24 days — of November were new record-setting high temperatures).

More Persistant, Intense Heatwaves

A marine heatwave (MHW) is defined as a period when there are 5 or more consecutive days when the observed SST is greater than the 90th percentile of the long-term average for that day. In the figure below, the long-term average is illustrated with the gray dashed line and the threshold for being a MHW day is illustrated by the dashed red line. The solid red line in the figure shows the observed SST for that day.

The Gulf of Maine met the criteria for MHW status for 353 days in 2022. While the warmest temperatures of the year were experienced in August (as we would expect from the climatology for the region), the largest temperature anomalies were observed during the last days of November, when they breached 7 °F above the long-term average.

A line chart shows the average sea surface temperature for each day of the year, and overlaid against it are notably smoother black lines representing the long-term mean, 10th percentile, and 90th percentile temperatures for those same days of the year. The area between the mean and the observed temperature is filled in with a solid color to indicate whether that day meets marine heatwave criteris. The observed temperatures for 2022 are above the 90th percentile for nearly the entire year, with the exception of two periods less than a week long in June and October.

Figure 9: A timeseries of marine heatwave (MHW) conditions in the Gulf of Maine extending from January 1 through November 30, 2022. Black lines representing the long-term (i.e., 1982 – 2011) average SST, the 10th percentile, and 90th percentile for a given day in the Gulf of Maine are labelled to indicate climatological reference points; a solid line (red for marine heatwave or blue for a non-event) indicate the observed SST this year; red and blue shading illustrates how far the observed SST falls from the climatological mean.

Comparing daily SST anomalies and MHW status for 2022 to the longer-term record — as in the figure below — it becomes clear that the frequency, duration, and intensity of MHWs has not only increased in the past decade, but reached a peak last year. Under historical levels of natural variability in the region, hot and cold SST anomalies tend to balance out within a year or over several years. What is being observed in the Gulf of Maine, however, is a loss of that balance: larger fractions of recent years are experiencing above average temperatures and cold spells are becoming vanishingly rare.

A figure displays the temperatures for each day of year as a colored stripe, organized with a row for each day such that the day of year aligns vertically. The lower two-thirds has a roughly equal balance between colors for warm (red) and cold (blue) temperature anomalies. The top third of the image is almost completely red as temperature anomalies rarely fall below the long-term average. Black dots are overlaid onto days that meet the criteria for a heatwave, they are rare in the lower section and common in the red section.

Figure 10: Heat map of daily SST anomalies from the beginning of 1982 through the fall of 2022. Not only do more large warm anomalies (darker reds) appear more frequently in recent years, but the frequency and duration of marine heatwave events (black lines) in the Gulf of Maine has become more pronounced in the past decade.

Warming Rate

GMRI research was the first to reveal that the Gulf of Maine has been warming faster than the vast majority of the world’s ocean. The figure below updates this historical analysis by including data for 2022. Indeed, the story has not changed: it’s clear that the Gulf of Maine is warming faster than ~98% of the world’s ocean. The reason why this is so important is because the rate of change can have profound consequences for the biology of individual species and for entire food webs. These aspects are areas of ongoing work (and captured well in the recent IPCC Working Group II report on impacts, adaptation, and vulnerability).

Figure 11: Maps of the northwest atlantic and global rate of warming displayed as their relative percentiles.

Concluding Thoughts:

In recent years, SSTs in the Gulf of Maine (and adjacent waters) have increased and the rate of warming has accelerated. Research suggests there are two major factors at play, one oceanographic and one atmospheric:

  1. Oceanographic: The Gulf of Maine is influenced by two primary oceanic currents: the Labrador Current and the Gulf Stream. Historically, there was a stronger southward flow of the Labrador Current. That stronger flow helped keep the heat transported northward along the U.S. east coast by the Gulf Stream further out to sea. More recently scientists have observed changes occurring in the interplay between the Labrador Current and Gulf Stream. More Arctic-origin freshwater from melting sea ice and land-based ice is constricting the southward flow of the Labrador Current. This is allowing the Gulf Stream to spread out more at lower latitudes around the Gulf of Maine. This then allows warmer water to “spill over” into the Gulf of Maine that otherwise would be kept further offshore.

  2. Atmospheric: The North Atlantic Oscillation — a large-scale pattern of natural variability in the atmosphere — has been in a “positive phase” more frequently over the past 10-15 years, meaning a more zonal (i.e., west-to-east) atmospheric pattern has dominated in the region. The relative decrease in “waviness” of the jet stream inhibits more consistent intrusions of cooler, Arctic air into the region. The relative contribution of these two climatological drivers may vary through time, but the result (in sea surface temperature terms) is similar: a warmer Gulf of Maine.

A Note on Data Sources

  • NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.highres.html.

Recommended Citation:

Gulf of Maine Research Institute. 2022. Gulf of Maine Warming Update: 2022 . https://gmri.org/stories/warming-22


OLD ASSETS:

Temperature Anomaly Horizons

One way to think about the severity of these changes is to think about temperature horizons. A temperature horizon captures how long temperatures remain above certain thresholds. Each threshold is designated its own temperature, and in this way we can see how long within a year temperatures remained: 1 to 2 or as much as 4\(^oC\) above normal.

Horizon plot of all years and their temperature anomaly horizons

Figure 12: Temperature anomaly horizons for all years of available satellite data (1982-2022). Horizons display how long temperatures were above certain thresholds (horizon width) and are colored by the strength of these events.

Comparing the Gulf’s Two Hottest Years

If we pull the horizons of our two hottest years on record it makes it easier to contrast where either one experienced acute high temperature events, and where there were sustained periods of above average temperatures.

Early into 2022 it was apparent that the year was on-par with the previous title-holder for warmest year on record.

Single year horizon plots comparing 2021 and 2022

Figure 13: Two horizon plots compare the timing and duration of elevated temperatures in the two warmest years on record, 2021 and now 2022. The width of a color horizon indicates the duration that temperatures were above that threshold.

Losing the Balance Between Hot and Cold

Another way to visualize the climate transition that we are observing is by looking at the fraction of each year spent in different temperature ranges. Under a steady climate we would expect over the long-term to spend similar amounts of the year experiencing relatively warm & cold temperatures. These periods would balance themselves out and we would on-average have experienced something similar to the long-term climate.

What we have been seeing in the Gulf of Maine recently has lost that sense of balance. Larger fractions of the year are shared by above average temperatures & cold spell events are becoming vanishingly rare.

Streamplot tracking fraction of each year spent in varying degrees of temperature anomalies

Figure 14: A streamplot shows the fraction of each year on record that temperature anomalies fell within ranges further from the climate reference period average. Since 2010 the Gulf of Maine’s temperatures shifted rapidly outside of this expected range and a large fraction of the year is now 2 degrees or more above that average (red).

 

A work by Adam A. Kemberling

Akemberling@gmri.org